This invention relates to the long-standing problem of the freezing over of the top of sewer vent pipes. The problem occurs during cold weather when relatively warm and relatively moist air and other gases rise upwardly through the sewer vent pipes and encounter below-freezing conditions. The problem is aggravated if concurrently there is precipitation, e.g., snow or sleet. The problem is universal in that it occurs in all areas of the world having cold climates.
Vent pipes are typically vertically oriented and extend upwardly through a roof structure, terminating with an opening through which the sewer gases, odors, etc., are intended to exit. The flow of the gases, etc., in the vent pipe is typically upwardly and also typically contains some water vapor.
During times when the outside or ambient air temperature falls below the freezing point, i.e., 32.degree. F., then it is possible for the aforesaid water vapor to accumulate in the form of ice on the inside of the sewer vent pipe, especially adjacent to the top opening thereof. As is well understood, the build up of ice can progress to the point where the sewer vent pipe is completely blocked off or sealed over by the build up of ice. Concurrently the build up can be aided by rain or snow which may be falling in the area. A complete blockage of the vent pipe can result in sewer gas entering the building; a very undesirable and sometimes dangerous condition.
Thus the problem is well known and long-standing, and there have been a number of prior art proposed solutions to the problem, none of which have been fully satisfactory, all things considered.
First of all, my co-pending U.S. patent application Ser. No. 08/806,170 filed Feb. 26, 1997, overcame a number of prior art problems but required a customized apparatus for each size of sewer vent pipe. To explain, those skilled in the art understand that there is quite a range of diameters of sewer vent pipes; vent pipes are frequently found in the range of 11/2inches, 2 inches, 3 inches, 4 inches, 5 inches and other. Further, some vent pipes are constructed of metal such as steel, while others are made out of plastic such as polyvinyl chloride (PVC).
Meyer, U.S. Pat. No. 4,524,262 has an elaborate and expensive defroster which is labor intensive in its installation. Also, there is no convenient means for knowing whether or not the system is operating.
Another prior art arrangement is Stadheim, U.S. Pat. No. 4,442,642; an insulating sleeve is positioned over a sewer vent pipe. This prior art arrangement has very low effectiveness against the build up of ice and, once a build up has occurred, there are no means for facilitating the removal thereof.
Behrens, U.S. Pat. No. 5,129,387 proposes the prevention of the formation of ice in a vent pipe by the gathering and focusing of solar radiation and distributing the radiation to the vent pipe in the form of heat in an attempt to provide an ambient temperature in the pipe above the freezing point of water. This approach, in addition to being costly, has some inherent and obvious limitations, i.e., long winter nights in areas having cold climates and the possibility of cloudy weather for obscuring the sunlight.
Yet another prior art apparatus is disclosed in Halone, Jr., U.S. Pat. No. 5,214,266 wherein an electric heating attachment is suspended at the top of a sewer vent and extends down within the sewer vent. This complex arrangement has not proven satisfactory.